1. Field of the Invention
The invention relates to a process for regenerating used articles of polyolefin to reusable raw material, in particular for regenerating used packaging foils made of polyethylene such as shrinking foils, bags and the like.
2. The Prior Art
Polyethylene is a polyolefin that is processed in large quantities for the manufacture of foils for packaging purposes. Articles such as, for example shrinking hoods, pouches and the like are manufactured from the foils.
Polyethylene, as a thermoplastic material, is repeatedly fusible and deformable due to its molecular structure. It is suitable for repeated reuse. However, any reprocessing to high-quality recycling products, preferably to PE foils with defined properties, is opposed by the fact that the used articles, in particular foils, are provided during their manufacture in an application-oriented way with additives such as antistatic agents, lubricants and thermo- or UV-stabilizers that are subsequently present in the recycling products manufactured therefrom in unknown quantities and combinations. Sorting of the used articles by ingredients is not possible for technical and economical reasons.
Recycling products, in particular foils loaded with such ingredients lead to problems in the course of their further processing, for example in the course of glueing, fusing or imprinting. Joining seams initially having good properties come apart in many cases only when in the user's hands.
In addition, the used foils contain degradation products such as non-polar PE waxes. The latter develop during the life time in the course of processing processes as well as due to the action of heat, light and weather. Such substances cause to some extent a considerable diminution of the properties of use of the recycling product, i.e., the foil.
Finally, the used foils, in particular packaging foils are imprinted to a greater or lesser extent. During the extrusion of regenerated materials to PE foils, such printing inks lead to a strong undefinable discoloration, so that only darkly dyed refuse bags can be manufactured from such materials.
Therefore, in order to be able to produce again high-quality foils from used polyethylene foil materials, it is necessary to removed from the used foils the foil additives, the non-polar PE waxes as well as the printing inks adhering thereto.